Optical image director



May 26, 1959 B. SCOTT ET AL OPTICAL IMAGE DIRECTOR Filed Feb. l1, 1954 United States Patent O OPTICAL IMAGE DIRECTOR Larkin B. Scott, New Canaan, and Edward L. McCarthy,

Glenbrook, Conn., assignors to The Perkin-Elmer Corporation, Norwalk, Conn., a corporation of New York Appueation February 11, 1954, serial No. 409,658

s claims. (c1. 9s4.s)

This invention relates to apparatus for redirecting light signals which may originate at any of an array of uniform co-planar areas. The present invention contemplates transmitting signals from such dispersed areas to a single common area. 1n one form, the invention may be employed as an improved photographic composing apparatus having a font, which may contain a large number of characters in a relatively small space without blank areas, and a novel optical system for imaging the characters of the font upon the same image spot on a light-sensitive element.

For a better understanding of the invention, reference may be made to the accompanying drawing, in which Fig. 1 is a diagrammatic View showing the action of the optical system of the apparatus;

Fig. 2 is a view in perspective, with parts broken away, of the essential features of the apparatus;

Fig. 3 is a view in elevation of the form of font plate employed in the apparatus of Fig. 2;

Fig. 4 is a fragmentary perspective view of a modified feature of the apparatus; and

Fig. 5 is a fragmentary diagrammatical view of the font plate used with the apparatus of Fig. 4.

The apparatus illustrated in Fig. 2 comprises a photosensitive element 10, upon which the characters employed in the composition are to be photographed in successive operations and which may be a strip of sensitized film, a photographic plate, etc. The element is shown as a plate mounted on a support indicated at 11 and, in an actual machine, conventional means are provided for moving the plate horizontally and for advancing it in the same way that a sheet of paper is moved and advanced in a typef writer.

The font of characters to be used in the apparatus is carried by a plate 12, which is opaque except for the characters 13, which are transparent. The surface of the plate is divisible into contiguous elemental areas, such as v the area 14 outlined by the dotted lines, and each area may contain a character. Means are provided for selectively passing light through the individual characters and such means may include a light box 1S having one side closed by the plate and its interior divided by opaque partitions 15a into individual cells lying behind respective characters on the plate. A light source 16 in the form of an electric lamp is then disposed within each cell and each lamp is in a circuit, which contains a battery 17 or other source of power and a normally open switch 18 closable by a key 19. There are thus as many keys as there are characters and the keys may advantageously be .arranged in la group like the key board on a typewriter. Instead of providing a lamp for each character, a single source of light may be employed within the box 15 and the passage of light through the individual characters may be controlled by shutters for the characters operated by the keys 19.

An optical system is disposed between the font plate 12 and the photo-sensitive element 10 for imaging the font plate characters upon a single image area on the photographic surface. This system comprises a lens 20, which lies in front of the font plate and which, if used alone, would produce upon element 10 inverted images of the characters in an array, which is the inverse of that upon the font plate. The system also includes a reflecting device 21, by which the images of all the characters are caused to be formed on the same image area on element 10. The reflecting device has a number of plane reflecting surfaces, not exceeding four, which lie in a closed series encircling the optical axis of the lens with the surfaces parallel to and equidistant from the axis. Preferably, the reflecting device is a prism, which may be either square or triangular in section, and the apparatus shown in Fig. 2 includes a prism 21a of square section with the length of a side of the square substantially equal to the aperture of the lens.

The shape of the elemental areas f the font plate employed in the apparatus varies with the cross-sectional shape of the prism 21a and, with a prism of square section, the font plate is made up of square elemental areas arranged in Vertical and horizontal rows, as in the plate shown in Fig. 3. The font plate in Fig. 3 is not square in outline, but has those elemental areas at its corners omitted which are not included within the permissible field angle of lens 20.

In the operation of the apparatus shown in Fig. 2, the illumination of a character on the font plate by depression of its key 19 causes a beam of light to pass through the character and the lens into the prism. If the character illuminated is the central character E lying on the lens axis, the lens produces an inverted image of the character on an image area on element 10, through the center of which the optical axis of the lens passes. Since the image of the character E is inverted, the character appears inverted on the font plate, so that the image will be that of the character erect and unreversed. Each character onplate 12 in an elemental area contiguous to the central area is imaged upon the photographic surface after the beam through the character has undergone one reflection. This will be apparent from Fig. 1, in which the beam B1 through the character B immediately above the central character E is caused by the lens to strike the bottom surface of the reflecting device 21 and is reflected by such surface to the image area on the photographic surface. Characters at other locations on the font plate are imaged uponthe photographic surface after the beams through the 'characters have undergone more than one reflection in the reflecting means 21, the number of such reflections being dependent upon the position of the character with respect to the central area, i.e., the number of spaces by which the character is removed from the central area. Thus, the beam B2 through the character Q on the font plate isireflected by both the bottom and top surfaces of the reflecting means before the character is imaged on the image spot on the photognaphic surface. The characters in the vertical and horizontal rows on the font plate, which include the character E, are imaged upon the photographic surface after their beams have been reflected one or more times by the opposed surfaces of the reflecting means. Characters, such as A, C, I, and G, which are obliquely displaced from the central character E, are imaged on the photographic surface after their beams have undergone reflections in each of a pair of reflecting surfaces lying at right angles to each other.

In order that the images of the characters appearing at the common area may be upright and unreversed, the aspects of the characters on the font plate must be varied in accordance with the locations of the characters on the plate in relation to the central character. The characters on the font plate may be divided into classes according to the orientation angle of the character, that is, the angle between the vertical axis of the character and the vertical, and to the reversal or non-reversal of the character, and the number of classes of characters is two times the number of directions of the reflecting surfaces in the reflecting device-21. Thus, if the system includes a prism square in section, there are four reflecting surfaces, two of which extend in one direction and two in another, and, with such a prism, the font plate willl have characters of four classes, namely, upright and unreversed, reversed, inverted, and both reversed and inverted.

in the selection of a lens and prism for use in the apparatus, the following considerations apply. The lens need be no greater than the cross-section of the reflecting device 21, since any portions of the lens projecting beyond the reflecting surfaces of the device serve no useful purpose. In order to utilize a large lens of high photographic speed, the reflecting surfaces must be separated a correspondingly relatively great distance, but, as the `separation of the surfaces is increased, the elemental areas containing the characters on the font plate are correspondingly increased in dimensions with the result that the characters in the outermost areas on the font plate lie at a large off-axis angle relative to the lens. If this angle is too great, the quality of the image is impaired.

ln the apparatus of the invention, the entire surface of the plate may carry characters, each in an elemental area, and there need be no blank areas on the plate. The number of characters, which the plate may carry, is a function of the f/number of the lens and of the halflield angle of the lens and the approximate number of characters may be determined by the following formula:

in which n equals the number of characters, F equals the quotient of the optical distance between the lens and element llt? divided by the effective aperture of the lens, and a equals the half-field angle of the lens. By calculation, it has been determined that the apparatus can ernploy a font plate having elemental areas for 250 characters and a lens of a speed of f/ 16 without seriously impairing the quality of the images of the characters `adjacent the margins of the plate.

in Fig. 4, there is illustrated a modification of the optical system, which differs from that shown in Fig. 2 only in that the prism 21a has been replaced by a prism 21h, which is an equilateral triangle in section. When such a triangular prism is employed, the elemental areas 14 on the font plate are triangular in shape. Since no two reflecting surfaces of the prism lie parallel, the surfaces extend in three directions and, as the classes of characters on the font plate must be twice the number of direc-y tions, the font plate used with the triangular prism must carry six classes of characters typified by the different positions of the character F on plate 12. It will be obvious that, in practice, all the characters in the font plate are dilerent from one another, but the character F has been shown on the plate 12' in order that the differences in orientation between characters in the different classes may be more readily understood. The character in each elemental area 14 is a mirror image of the character in each of the contiguous elemental areas and this same relation prevails among the characters on font plate i2, in which the elemental areas are squares.

We claim:

l. An apparatus of the character described for selectively transmitting dierent images to a common area comprising a flat plate having a plurality of characters thereon, some of said characters being positioned at different radial distances from a point on said plate, reecting optical means having its optical axis aligned with said point and normal to said plate, said optical means including a plurality of reflective plane surfaces disposed parallel with the optical axis thereof and forming an equilateral polygon in cross section, focusing means located between said plate and said reflecting optical means, the optical axis of said focusing means being coincident with the optical axis of the reflecting optical means and means to selectively illuminate each character whereby images thereof are transmitted to said area.

2. The apparatus as defined in claim l in which said reflecting optical means comprises mirrors disposed about the major axis thereof;

3. The apparatus as defined in claim l in which said reflecting optical means comprises a square prism and said reflective plane surfaces comprise the surfaces of said prism.

4. The apparatus as defined in claim l in which said reflecting optical means comprises a triangular prism and said reflective plane surfaces comprise the surfaces of said prism.

5. An apparatus of the character described for selectively projecting different images to a common area comprising a flat plate having a plurality of transparent characters thereon, said characters being positioned at different radial distances from a central point on said plate, reflecting optical means having its optical axis aligned with said central point and normal to said plate, said optical means including a plurality of reflective plane surfaces disposed parallel with the optical axis thereof and forming an equilateral polygon in cross section, lens means interposed between said plate and said reflecting optical means, the optical axis of said lens means being colinear with the optical axis of the reflecting optical means whereby images of said characters are directed through said reflecting means, the number of reflections of each image being a function of the radial distance of the respective transparent character from the central point of said plate, each of said transparent characters being oriented in accordance with the number of reflections of the image thereof and means to selectively produce projecting light rays from each transparent character.

6. The apparatus as defined in claim 5 in which said reflecting optical means comprises mirrors disposed about the major axis thereof.

7. The apparatus as defined in claim 5 in which said reflecting optical means comprises a square prism and said reflective plane surfaces comprise the surfaces of of said prism.

8. The apparatus as defined in claim 5 in which said reflecting optical means comprises a triangular prism and said reflective plane surfaces comprise the surfaces of said prism.

References Cited in the le of this patent UNiTED STATES PATENTS 1,523,992 Hadley Jan. 20, 1925 1,577,388 TWyman Mar. 16, 1926 1,712,431 Hadley May 7, 1929 1,944,1ll Schieren Jan. 16, 1934 2,663,232 Drillick Dec. 22, 1953 FOREIGN PATENTS 63,274 France May 31, 1864 711,918 France July 8, 1931 

